I used a remote camera device for the FlyCamOne (FC02) with the modified CHDK Firmware on the Canon to get remote shutter working through a USB lead, it needs 5v on pins 1 and 4.
All worked well until I connected the video out for the camera, I found that the FC02 switched the ground not the live, the video jack is grounded so when plugging that in triggers the shutter.
I made this simple circuit with an old transistor to change this around.